feat(token-2022/metadata): add pinocchio example

[MarkFeder]

What

Adds a Pinocchio implementation of the Token-2022 metadata example (the anchor example has no native sibling), following the same kit + litesvm template as the other Token-2022 pinocchio examples. This is the last of the token-2022 mint extensions.

How it works

The single instruction creates a mint that stores its own on-chain metadata:

1. CreateAccount — sized for the base mint + the fixed-length MetadataPointer extension (234 bytes).
2. InitializeMetadataPointer (wrapper 39) — points the mint at itself as the metadata account.
3. InitializeMint2 (20) — decimals 2, payer as mint authority.
4. System Transfer — tops up the mint's lamports so it stays rent-exempt after the metadata realloc.
5. TokenMetadataInitialize — the SPL Token Metadata interface instruction (Token-2022 implements it), which reallocates the mint to fit and writes name/symbol/uri.

Two things worth noting:

• The metadata interface dispatches on an 8-byte SPL discriminator (sha256("spl_token_metadata_interface:initialize_account")[..8]), not the 1-byte Token-2022 variants.
• The metadata is variable-length, so the account can't be fully sized up front — hence the realloc (done by the CPI) and the rent top-up (done here). The program forwards the Borsh-encoded name/symbol/uri from its instruction data verbatim after the discriminator.

Test

litesvm + @solana/kit. The test encodes name/symbol/uri, invokes the program, then decodes the mint with the official @solana-program/token-2022 codec and asserts the MetadataPointer points at the mint and the TokenMetadata holds the expected fields.

Token-2022 Metadata (Pinocchio)
  ✔ Creates a Token-2022 mint with on-chain metadata
1 passing

Verified locally: cargo build-sbf, the litesvm test, tsc --noEmit, Prettier, cargo fmt --check, Clippy, and pnpm install --frozen-lockfile all clean. (The deploy script uses the *.so glob per #702.)

---

AI use: I directed the design (the CPI sequence, the realloc + rent top-up, the instruction-data passthrough) and verified every encoding against the spl-token-2022-interface / spl-token-metadata-interface sources; implementation and tests were written with Claude Code and reviewed by me.

[greptile-apps]

Greptile Summary

The PR adds a Pinocchio implementation of the Token-2022 metadata example.

• Creates and funds an extended Token-2022 mint through System Program and Token-2022 CPIs.
• Initializes a self-referencing metadata pointer and variable-length on-chain metadata.
• Adds a LiteSVM test that validates the mint and extensions with the official Token-2022 codec.
• Registers the program in the Cargo workspace and adds package, lockfile, build, and deployment configuration.

Confidence Score: 5/5

The PR appears safe to merge; no concrete changed-code defect or security issue was identified.

The implementation keeps extension initialization order, serialized layouts, CPI account roles, account sizing, and rent funding aligned, while the end-to-end test validates the resulting mint with the official Token-2022 decoder.

Important Files Changed

Filename	Overview
tokens/token-2022/metadata/pinocchio/program/src/instructions/create_mint.rs	Implements the mint lifecycle, fixed program CPIs, rent top-up, and metadata initialization with internally consistent account and serialization layouts.
tokens/token-2022/metadata/pinocchio/program/src/instructions/mod.rs	Defines the Token-2022 program ID, extended mint size, and decimal configuration used by the implementation.
tokens/token-2022/metadata/pinocchio/program/src/processor.rs	Forwards the single instruction's Borsh metadata payload to the mint creation handler.
tokens/token-2022/metadata/pinocchio/tests/test.ts	Exercises the complete LiteSVM flow and validates ownership, account size, mint fields, metadata pointer, and token metadata.
tokens/token-2022/metadata/pinocchio/package.json	Adds build and test commands plus dependencies pinned by the committed pnpm lockfile.
Cargo.toml	Registers the new Pinocchio metadata program as a workspace member.

_{Reviews (1): Last reviewed commit: "feat(token-2022/metadata): add pinocchio..." | Re-trigger Greptile}

[MarkFeder]

@amilz could you take a look at this one when you get a chance?

No open review threads left on it, so it is ready for maintainer review. It is one of 23 open Pinocchio ports I have up — they are independent and self-contained, so they can be reviewed and merged in any order: https://github.com/solana-developers/program-examples/pulls/MarkFeder